1. Field of the Invention
The present invention relates to a leading vehicle detecting apparatus and an inter-vehicular control apparatus using the leading vehicle detecting apparatus. To put it in concrete terms, the leading is vehicle detecting apparatus and the inter-vehicular control apparatus may be mounted in a vehicle including an adaptive cruise control (ACC) system. The inter-vehicular control may be executed by using an inter-vehicular controller therein. The ACC system controls the inter-vehicular distance between the own vehicle and a leading vehicle when the own vehicle is traveling such as to follow a leading vehicle (a vehicle traveling directly in front of the own vehicle) traveling in the same traffic lane as the own vehicle, among the vehicles (preceding vehicles) traveling ahead of the own vehicle.
2. Description of the Related Art
In recent years, vehicles are being provided that include ACC system as a system for reducing driving load placed on drivers. The ACC system automatically controls the traveling speed of the vehicle to a set speed, and automatically controls the inter-vehicular distance between the own vehicle and a leading vehicle traveling ahead of the vehicle to a predetermined distance. In other words, when the speed of the leading vehicle is slower than the set speed, the ACC system performs control to operate the brakes or the like and decelerate the own vehicle to ensure the predetermined inter-vehicular distance. When the leading vehicle moves further ahead, the ACC system performs control to accelerate the own vehicle to the set speed.
In a technology, such as that described above, for controlling the distance from the leading vehicle, a judgment is required to be made regarding whether or not the leading vehicle is a suitable candidate to be followed. As a technology for making such judgments, a technology is known in which the probability of a vehicle traveling ahead of the own vehicle being suitable to be a leading vehicle is calculated by a traffic lane probability map, using relative positions of the own vehicle and the leading vehicle, and a presumed course (presumed cruising track) of the own vehicle. The judgment is then made based on the calculated probability (refer to, for example, JP-A-2008-269007).
However, a difference may occur in the presumed course of the own vehicle and the course of the leading vehicle on, for example, a curved road because of the difference in the positions of the own vehicle and the leading vehicle on the curved road on which they are traveling. In this instance, in the technology described in JP-A-2008-269007, the probability of a judgment being made that the vehicle traveling ahead of the own vehicle is the leading vehicle is low. Even when the vehicle is the leading vehicle that is traveling in the traffic lane (referred to, hereinafter, as a “cruising lane”) in which the own vehicle is traveling, a judgment is likely to be erroneously made that the vehicle is not the leading vehicle. When such erroneous judgment is made, the own vehicle accelerates regardless of the leading vehicle being present, thereby causing the driver of the own vehicle to experience discomfort regarding the movement of the vehicle.
Conversely, on a curved road or the like, a judgment may be erroneously made that a vehicle traveling in a traffic lane other than the current lane, such as a traffic lane adjacent to the cruising lane, is the leading vehicle. When such erroneous judgment is made, the own vehicle excessively decelerates regardless of a leading vehicle not being present, thereby causing the driver to experience discomfort regarding the movement of the vehicle in a manner similar to that described above.
As a method of judging, without error, whether or not a vehicle traveling ahead of the own vehicle on a curved road and the like is a leading vehicle to be followed, a method is known in which the judgment is made regarding whether or not the vehicle is the leading vehicle at a position near the own vehicle. However, when the position at which the judgment is made is placed nearer to the own vehicle, leeway in terms of time for performing speed control of the own vehicle after the judgment becomes small. Therefore, gradual deceleration becomes difficult, and passengers in the own vehicle may experience discomfort. In other words, a problem occurs in that achieving both improved judgment accuracy regarding a leading vehicle and gradual deceleration of the own vehicle becomes difficult.
Hence, a leading vehicle detecting apparatus and an inter-vehicular control apparatus using the leading vehicle detecting apparatus capable of suppressing delay in judgment timing regarding a judgment of whether or not an own vehicle is following a preceding vehicle traveling in a same traffic lane as the own vehicle, while maintaining judgment accuracy, is desired.